In recent years, with the incessant improvement of the liquid display technique, liquid display products gradually enter into various fields of application. With advantages such as low energy consumption, flatness, light and thin structure, highly efficient display, energy saving, being environmentally friendly and the like, liquid crystal displays have taken a very significant role in the field of display.
With the incessant progress of the liquid display technique, the technique of cholesteric liquid crystal (CLC) display, which is novel, lighter and thinner, has low energy costs and portable, has been proposed. A cholesteric liquid display is characterized by high brightness of reflection, wide viewing angle, and low energy consumption, and enables display on a flexible substrate. A cholesteric liquid crystal display employs a reflective mode, and thus it is possible to omit a backlight and reduce the energy consumption and volume of an electric display device. Reflective cholesteric liquid displays can be widely used for occasions that require display but not frequent refreshing, such as e-books, e-curtains, price tags, outdoor advertisements, and the like.
CLC has drawn interest from many researchers due to its unique characteristics derived from its structure. The most important characteristics of CLC include its selective reflection property: circularly polarized light that shares the same optical direction as the helical axis of the CLC is reflected, while other light penetrates. For normal incoming light, the equation for the wavelength at the maximum selective reflectance is λ0=n•p, wherein n is an average reflection coefficiency, and p is a pitch. Although is an inherent property of a liquid crystal molecule, p varies along with temperature, electric field strength, magnetic field strength and the like. Therefore, it is possible to select the color of the reflected light by adjusting p. As early as 1989, Bmer et al. controlled the p of the cholesteric liquid crystal molecule through ultraviolet (UV) light sensitive materials (Bmer, J Bovcn, and GN Mol, Macromol Chem, 190, 2255 (1989)).
In the past ten plus years, it has been difficult to achieve full color display with a single layered CLC. The conventional method for full color display is to stack the single layered CLCs that each can reflect a single wavelength (such as red light, green light and blue light) (A. A. Khan, X.-Y. Huang, H. Yuan, M. Lu, and E. C. Urban, U.S. Pat. No. 6,377,321 (2002)). However, this will greatly increase costs and limit the practical use of the method.